Anthropic launched Fable 5.1 at the same $10/$50 list price but cut cache reads 75%. Here is what shipped, what it costs, and what it means for agents.
Key takeaways
- On September 1, 2026, Anthropic released Claude Fable 5.1 and a gated variant, Mythos 5.1, keeping Fable 5's $10 input and $50 output list price per million tokens.
- The one price that moved is cache reads, cut 75% to $0.25 per million, which Anthropic estimates lowers typical workloads about 25% and highly agentic ones up to about 45%.
- On Anthropic's launch benchmarks, Fable 5.1 now leads both Fable 5 and Opus 5 on all seven, most dramatically on Terminal-Bench-Science, at 52.6% versus Fable 5's 24.7% and Opus 5's 29.0%.
- Mythos 5.1 is the same model with different safety filters, offered under restricted access for vetted cybersecurity and life-sciences organizations.
- Van Data Team's recommendation: if you run Fable 5, upgrade for the cache savings; if you run Opus 5, weigh capability against Fable's double token price, measured on your own real tasks rather than a launch table.
📖 Read the full guide on Van Data Team → Claude Fable 5.1: Same Price, 75% Cheaper Cache
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